Can anyone give me a link to some research (I think one was carried out in Tayside) papers that show low TSH doesn't necessarily lead to increased risk of AF and stroke? I had been having palpitations and had a dizzy spell before Christmas so I had my bloods done by my GP. I think she will be trying to reduce my Levo dose from 100 to 75 as TSH is suppressed but the last time I was on 75 I felt terrible. I feel I need to be seen by an endo as none of my figures make sense. Here are the latest test results on 100mcg Levo -
TSH 0.09 (0.35-5)
T4 16.159% through range 9.0-21.0
T3 4.137% through range 3-6
These results are similar three other tests carried out between 30 June and 28 December 2021.
Vitamin and mineral levels also tested but results not yet available.
The last time I was on 75 my results were -
TSH 1.11 (0.35-5)
T4 14.647% through range 9.0-21.0
T3 wasn't tested as I was in normal range for TSH
I have GP and another doctor telling me I am at risk of AF and stroke If I stay on 100mcg of Levo and yet T4 and T3 levels are poor and there are numerous papers cited saying below range TSH is OK when medicated. I notice that Dr Anthony Toft's paper states that 'This 'exogenous subclinical hyperthyroidism' is not dangerous as long as serum T3 is unequivocally normal – that is, serum total around T3 1.7nmol/l (reference range 1.0-2.2nmol/l)' i.e. around 60% through the range my T3 is around half of what Toft would recommend so does that mean I am at risk of AF and stroke?
I am also not sure if my palpitations are due to the doctors worrying me!!
Please help . Thank you
Written by
Piglet1956
To view profiles and participate in discussions please or .
Always test thyroid levels as early as possible in morning before eating or drinking anything other than water and last dose levothyroxine 24 hours before test
Do you always get same brand levothyroxine at each prescription …if yes….. which brand
What vitamin supplements are you currently taking
Looking at previous posts you have high thyroid antibodies and autoimmune thyroid disease confirmed
Thank you SlowDragon. All tests carries out 24 hours after last Levo dose and either at 9 or 9:30am (most recent was at 9:30am). I am not celiac but Im strictly gluten free. My antibodies are around 178 at the moment, reduced from around 1100 when first diagnosed 18 months ago so I feel pleased about that. Do you have a source that I can quote for low T3 also causing palpitations?
Interestingly, patients with a serum TSH below the reference range, but not suppressed (0.04–0.4 mU/liter), had no increased risk of cardiovascular disease, dysrhythmias, or fractures. It is unfortunate that we did not have access to serum free T4 concentrations in these patients to ascertain whether they were above or within the laboratory reference range. However, our data indicate that it may be safe for patients to be on a dose of T4 that results in a low serum TSH concentration, as long as it is not suppressed at less than 0.03 mU/liter. Many patients report that they prefer such T4 doses (9, 10). Figure 2 indicates that the best outcomes appear to be associated with having a TSH within the lower end of the reference range.
Dr Toft, past president of the British Thyroid Association and leading endocrinologist, states in Pulse Magazine,
"The appropriate dose of levothyroxine is that which restores euthyroidism and serum TSH to the lower part of the reference range - 0.2-0.5mU/l.
In this case, free thyroxine is likely to be in the upper part of its reference range or even slightly elevated – 18-22pmol/l.
Most patients will feel well in that circumstance.
But some need a higher dose of levothyroxine to suppress serum TSH and then the serum-free T4 concentration will be elevated at around 24-28pmol/l.
This 'exogenous subclinical hyperthyroidism' is not dangerous as long as serum T3 is unequivocally normal – that is, serum total around T3 1.7nmol/l (reference range 1.0-2.2nmol/l)."
You can obtain a copy of the articles from Thyroid UK email print it and highlight question 6 to show your doctor
Thank you for this - I've recently had my dose reduced for a suppressed TSH, due a risk of osteoporosis and I've been meaning to research the risk. This article is a great first step.
I always have TSH at 0.02 with T4 over the top. I have recently added in some T3 as my range is very low. I have AF but have discussed my range with my cardiologist and she was not at all bothered.
'This 'exogenous subclinical hyperthyroidism' is not dangerous as long as serum T3 is unequivocally normal – that is, serum total around T3 1.7nmol/l (reference range 1.0-2.2nmol/l)' i.e. around 60% through the range my T3 is around half of what Toft would recommend so does that mean I am at risk of AF and stroke?
This is a bit confusing. When Toft says 'normal', he means somewhere within the range, be it 60%, 30%, 5% or whatever. By 'abnormal' he would mean over-range.
Also, Toft is talking about Total T3. Your result is a Free T3, so not the same thing, and can't be compared in any way.
So, no, your results in no way suggest that you are at risk of AF or stroke, even with a suppressed TSH.
Now I am confused . So when Toft talks about most people feeling well when both T4 and T3 are in the upper part of the reference range he is referring to free T4 but Total T3? 🤦♀️😕And how would I ever know what my Total T3 is?
Apparently so, yes. Toft is Scottish, and in Scotland they test the TT3 rather than the FT3, I'm lead to believe. In the rest of the UK, they test the FT3, if they test T3 at all. But, you really don't need to know what your TT3 is, it's a pretty useless test, don't know why they do it.
I'm in Scotland and all my lab results are definitely for Free T3. But I guess TOFT may may have worked differently. I only get my FT3 tested when TSH is below the reference range!!
I'm in Scotland too and the only TT results I ever had were from an endo. GP labs are always FT. Also FT3 tests were stopped in Oct 2001 unless TSH suppressed....which it is permanently because I'm on high dose T3-only!!
Dear Dippy Dame, what do you call suppressed. I have TSH at .005 but my T3 and T4 are always mid range. I am on 100 levo and 10mg Lio. Many thanks. Susie
"Suppressed" is considered to be a result below the TSH reference range....but medics are far too reliant on TSH labs, I'll explain below.
I'm on high dose T3-only because I have a type of Thyroid Hormone Resistance and my TSH is on the floor because the pituitary recognises the high hormone level in the blood and sends a signal ( low TSH) to tell the thyroid gland to produce less hormone.
But...
TSH is not a reliable test on which to base dosing it does not show us the level of free T4 and T3 which we need as a guide to dosing. FT3 is the important lab, it is the active thyroid hormone required by every cell in the body in an adequate and constant supply.
I would rely on thyroid hormone levels FT4 and FT3 labs as a dosing guide....not the pituitary hormone level TSH.
If FT3 is in range you are very unlikely to be overmedicated.
If you feel well on your current dose don't be persuaded to change it on the basis of TSH!
Thank you DippyDame. My current TSH is 0.09, FT4 is 59% through the range and FT3 37% through the range. Even with these I still have some hypo symptoms but new and the most worrying is palpitations mostly at night. I fear they will want me to reduce Levo from 100mcg to 75mcg without addressing the other symptoms.
Common variation in the DIO2 gene predicts baseline psychological well-being and response to combination thyroxine plus triiodothyronine therapy in hypothyroid patients
Vijay Panicker 1, Ponnusamy Saravanan, Bijay Vaidya, Jonathan Evans, Andrew T Hattersley, Timothy M Frayling, Colin M Dayan
FT4 at 59% is still slightly on the low side....some/most people will need it to be higher
FT3 at 37% is far too low and most likely why you are having palpitations etc
You'll remember that FT3 is the important result and that every cell in the body needs to be saturated with an adequate and constant supply of T3....if T3 is low we suffer!
Important to ensure vit D, vit B12, folate and ferritin are optimal ...to support thyroid function
You could increase to 125mcg levo though I suspect this may still not produce enough T3....don't let them reduce your levo. Your FT3 will just drop further. Don't accept scaremongering about low TSH!
Then retest in 6 weeks...
Or, in your shoes, based on poor T4 to T3 conversion, I'd straight away push for the addition of T3....maybe 10mcg added to your 100mcg Levo.
For good health both Frees need to be somewhere approaching 75% through their respective ranges.
GPs don't initiate T3 medication so your best approach may be to ask for referral to an endo....and hope they are knowledgeable!
Thank you again. I have a phone call with GP tomorrow which I’m dreading. Not had the thyroid convo with this particular one but no reason to expect she will be different to the others. I will have the DIO2 test done. Did you see an endo on NHS?
Yes, I saw an NHS endo twice but it soon became clear he wasn't able to help me, so with the support of some experienced members here I decided to take control...lovely man but knowledge poor. He would never in a million years have prescribed the dose of T3 I need to function.
It turned out that I'm a fairly rare case ( it was a steep learning curve!) so don't let my experience put you off requesting an endo appointment...they should be able to help
You have every right to ask for a referral. While you wait for an appointment, it might take time, so ask this GP if she will consider giving you a trial of 125mcg ( "trial" dents their ego less than asking outright for more!!), that may help a little until you get some T3.
Hopefully this new GP is open minded ...quietly and politely stick to your guns. It's your health and we ( you) know our bodies better than anyone else...and yours is telling you it needs help! Use the info we've given you to state your case.
Make a list of what you want to ask/ say before you speak to this GP....that used to help me focus.
I went through something similar last year where my TSH was under range 0.09 and levo reduced from 100 to 75 even though I protested. During the year I was also having issues with menopause and HRT. But to cut a long story short I had an appointment with GP in November and strongly put my case to which she said she'd write to Endo and I've now had my levo increased only slightly 100 & 75 alternate days. By the time this change happend my TSH was up to 2.3 in less than 12 months! Glad I protested.
Thank you so very much for this. Enormously helpful - have just tried to absorb it. I still have symptoms so maybe I need to experiment with other methods/medication.
My surgery gives TT3 results (rarely, but when the lab deigns to test T3 it's total rather than free). I'm in the Glasgow area.Dr Toft stated (it was in a video I watched on YouTube) that he thought Total T3 was the more useful test, actually, although I know that's an unpopular opinion around here!
Effects of Long-Term Combination LT4 and LT3 Therapy for Improving Hypothyroidism and Overall Quality of Lifencbi.nlm.nih.gov/pmc/articl...
"None of the patients who had abnormally low TSH or elevated FT3 or FT4 levels had hospitalizations for arrhythmias or thyrotoxicosis."
I'm a thyroid cancer survivor, total thyroidectomy and my TSH has been undetectable for several years now. I do well with FT4 in the lower end of range and FT3 in the upper 75+ % of range.
That’s good to hear that you’re feeling well. Gives me hope. My sense is exactly what you and DippyDame and others suggest ie T3 is too low but I don’t know where to begin on that one.
I take 2 grains of NDT (NP Thyroid brand) a day and occassionally take additional synthetic T3. I am in the US – my nurse practitioner orders my tests (TSH, FT4, FT3 and cancer markers calcitonin and CEA) and prescribes my meds. I long ago gave up on endos but did work with my cardiologist on finding a reasonably optimal dose. It was a lot of work - I tracked my hear rate and blood pressure, along with energy levels, several times a day for a few months while we experimented with different dosing that didn't worsen my pre-existing cardiac issues (chronic tachycardia) while keeping me functional.
Despite being a nurse I knew almost nothing about thyroid until I got thyroid cancer. I found most endos I encountered knew even less while many NP's, who work a lot with women's issues, are more up to date and understanding and actually understand how thyroid hormones work.
Content on HealthUnlocked does not replace the relationship between you and doctors or other healthcare professionals nor the advice you receive from them.
Never delay seeking advice or dialling emergency services because of something that you have read on HealthUnlocked.
TSH low the rest normal
Endo consultation today for low TSH
Low T3 Low T4 and very Low TSH
Low TSH on no meds - should I be concerned or not?
normal TSH and T3 but Low T4
